10.2 A 28nm HPM heterogeneous multi-core mobile application processor with 2GHz cores and low-power 1GHz cores

Abstract

The worldwide demand for high-performance mobile or car infotainment application processors (AP) is increasing. This demand coexists with the need for low power to achieve long battery life and avoid thermal runaway. A heterogeneous CPU configuration is an effective solution. The proposed heterogeneous quad/octa-core AP has a combination of high-performance 2GHz cores and energy-efficient 1GHz cores. The maximum performance in the octa-core configuration is 35600 DMIPS. The key design highlights are: 1) Using a dedicated PLL and H-tree clock in the high-performance CPU achieves both 2GHz operation and reduced dynamic power. 2) A low-leakage SRAM in a 28nm HPM process is used and the leakage current of the peripheral circuits of the SRAM macro is optimized via multiple threshold voltages (Vt) and gate lengths (Lg). 3) The effects of process and voltage variations are accurately corrected by an on-chip process sensor and direct sensing of the voltage in the power mesh of the chip. 4) An enhanced CPU clock control mechanism is employed, which uses an on-chip delay sensor to reduce AC IR drop. 5) The heterogeneous CPU architecture maintains high performance even during thermal throttling.